Varicose veins are enlarged, tortuous and often blue in color and commonly occur in the legs below the knee. Varicose veins are the most common peripheral vascular abnormality affecting the legs in the United States. Varicose veins often lead to symptomatic venous insufficiency. Greater saphenous vein reflux is the most common form of venous insufficiency in symptomatic patients and is frequently responsible for varicose veins in the lower leg. This occurs in about 25% of women and about 15% of men.
All veins in the human body have valves that when functioning properly, open to allow the flow of blood toward the heart and close to prevent backflow of blood toward the extremities. The backflow of blood is also known as reflux. The venous check valves perform their most important function in the veins of the legs where venous return flow is most affected by gravity. When the venous valves fail to function properly, blood leaks through the valves in a direction away from the heart and flows down the leg in the wrong direction. The blood then pools in the superficial veins under the skin resulting in the bulging appearance typically seen in varicose veins. The pooling of blood in the leg veins tends to stretch the thin elastic walls of the veins, which in turn causes greater disruption in the function of the valves, leading to worsening of the varicosities. When varicose veins become severe, the condition is referred to as chronic venous insufficiency. Chronic venous insufficiency can contribute to the development of pain, swelling, recurring inflammation, leg ulcers, hemorrhage and deep vein thrombosis.
Traditionally, varicose veins have been treated by a surgical procedure known as stripping. In stripping, varicose veins are ligated and completely removed. More recently, varicose veins have been treated by endovenous laser therapy. Endovenous laser therapy treats varicose veins of the leg by eliminating the highest point at which blood flows back down the veins, thereby cutting off the incompetent venous segment. Endovenous laser therapy has significant advantages over surgical ligation and stripping. In general, endovenous laser therapy has reduced risks related to anesthesia, less likelihood of surgical complications, reduced costs and a shorter recovery period than ligation and stripping.
Endovenous laser therapy involves the use of a bare tipped or shielded tip laser fiber to deliver laser energy to the venous wall from within the vein lumen that causes thermal vein wall damage at the desired location. The subsequent fibrosis at this location results in occlusion of the vein that prevents blood from flowing back down the vein. Generally, endovenous laser therapy utilizes an 810 to 980 nanometer diode laser as a source of laser energy that is delivered to the venous wall in a continuous mode with a power of about 10 to 15 Watts.
An exemplary endovenous laser therapy procedure is disclosed in U.S. Pat. No. 4,564,011 issued to Goldman. The Goldman patent discloses the use of an optical fiber to transmit laser energy into or adjacent to a blood vessel to cause clotting of blood within the vessel or to cause scarring and shrinkage of the blood vessel.
A typical endovenous laser therapy procedure includes the location and mapping of venous segments with duplex ultrasound. An introducer sheath is inserted into the greater saphenous vein over a guidewire, followed by a laser fiber about 600 micrometers in diameter. The distal end of the laser fiber is advanced to within 1 to 2 cm of the sapheno-femoral junction. Laser energy is then applied at a power level of about 10 to 15 watts along the course of the greater saphenous vein as the laser fiber is slowly withdrawn. Generally, positioning of the laser fiber is done under ultrasound guidance and confirmed by visualization of the red aiming beam of the laser fiber through the skin. The application of laser energy into the vein utilizes the hemoglobin in red blood cells as a chromophore. The absorption of laser energy by hemoglobin heats the blood to boiling, producing steam bubbles which cause full thickness thermal injury to the vein wall. This injury destroys the venous endothelium and creates a full-length occlusion and destruction of the greater saphenous vein. An example of current techniques for endovenous laser therapy procedures is described in U.S. Patent Publication No. 2003/0078569 A1, the disclosure of which is hereby incorporated by reference.
While current endovenous laser therapy procedures offer a number of advantages over conventional ligation and stripping, challenges remain in successfully implementing an endovenous laser therapy procedure. The accurate localization of the bare distal end of the laser fiber can be difficult even with ultrasound assistance. In addition, a bare distal end of the laser fiber is transparent to fluoroscopy. Because of the relatively small diameter and sharpness of the laser fiber, the distal tip of the laser fiber can sometimes enter or puncture and exit the vein wall while the laser fiber is being advanced up a tortuous greater saphenous vein. Laser fibers used in current endovenous laser therapy procedures are glass optical fibers coaxially surrounded by protective plastic jacket or coating.
In current endovenous laser therapy procedures, a laser fiber is inserted into a vein while sheathed in a catheter. Because of the relative stiffness of the laser fiber and the fact that it is formed from glass, and the relatively sharp distal end of the laser fiber, the catheter allows for easier advancing of the laser fiber through the blood vessel. When the laser fiber-catheter combination has reached a desired location, typically slightly proximal from the sapheno-femoral junction, the laser fiber is advanced to extend beyond the distal end of the catheter by a significant distance. Laser energy is applied through the optical fiber and the catheter and laser fiber are withdrawn at the same time that the laser energy is applied.
An alternative approach includes placing a guidewire in the blood vessel, advancing the guidewire until it is in a desired location, then advancing a laser fiber which includes a structure for engaging the guidewire, along the guidewire until it is at the desired location, withdrawing the guidewire and then withdrawing the laser fiber while simultaneously applying laser energy to the blood vessel. In either case, these procedures require the insertion and removal of multiple structures into and out of the blood vessel. These multiple insertions and removals take time, and may also increase the likelihood of possible unintended injury or perforation of the blood vessel during the procedure.
Thus, there is still room for improvement to endovenous laser procedure and apparatus.